1. Field of the Invention
The present invention relates generally to an optical signal-transmission system for an automotive vehicle, and more particularly to an optical signal-transmission device such that a number of electric control signals generated from switches arranged on the steering wheel are transferred digitally and optically to other controllers to control the vehicle operating conditions with a high reliability without producing electrical noise, even when the steering wheel is freely turned.
2. Description of the Prior Art
As is well known, there is a need to generate a number of control signals from switches arranged on the steering wheel and to transfer these signals to other control systems provided on the vehicle body, such as an automatic speed cruise control device (ASCD).
Although described in more detail hereinafter, when a mechanical signal-transmission device is used for this purpose it is necessary to arrange a sliding contact mechanism including for instance slip rings and sliding contact points in a relatively small area behind the steering wheel. In this mechanism however there are a number of problems or shortcomings; for example it is difficult to increase the number of switches since the area behind the steering wheel is too small to accommodate many slip rings; the sliding contact mecanism is readily affected by fluctuations of the supply voltage; chattering of the contact points or electrical noise caused by the contact points is inevitable, thus reducing the reliability and limiting the increase of the use of such control signals.